The posture taught by the PE teacher is: supine, feet together, fingers crossed behind the head. Then sit up once, with your head touching your knees, just once. Sitting up depends on the rhythm of breathing, sucking before sitting up and breathing after sitting up. The stress point is in the abdomen, and the hand behind the head should be harder. Your feet should be close together, or ask another person to press them for you. It used to be a two-person test. Don't do too much exercise at once. Do 10 exercise first. About a week later, add five more exercises, and so on, step by step. When you can do it for about 40 times in a row, you start to practice timing. You can do it more than 50 times a minute, and your waist strength is not bad. Keep practicing every day. If you stop for one day, you have to make up for a few days. I wish you success in your exam!